var swfu; 
var init_uploader = function() { 
    swfu = new SWFUpload({ 
        upload_script : upload_url, 
        target : "SWFUploadTarget", 
        flash_path : swfupload_url 
        //many more options which you must determine for yourself - see the SWFUpload docs and examples 
    }); 
    swfu.loadUI(); 
}; 

//please use better handler attachment than this: 
window.onload = init_uploader; 